1. Field of the Invention
The present invention relates to a flap deploying drive assembly. More particularly, the invention relates to a flap drive system for an aircraft having at least one linear drive assembly for linearly extending a deployably mounted flap section and at least one dynamic structure for rotationally positioning the flap.
2. Discussion of the Prior Art
The extension and positioning of flaps during flight requires mechanisms which are capable of withstanding considerable aerodynamic stresses with little tolerance for error. It is clearly understandable that the reliable functioning of such flaps is critical to the safe operation of aircraft. Present flap drive systems which exist in the prior art generally comprise either wide so-called "canoes" along which the extending flap are motively translated or complex assemblies having a considerable number of components and requiring a large housing volume within the airfoil. The number of components and volumetric requirements are considerable drawbacks for the practical applications of these designs.
In addition, the "canoes" have the important shortcoming of presenting a large aerodynamic cross-section, also known as "blockage", to the air which passes between the extended flap and the airfoil. The free flow of this air is critical because it reenergizes the airflow as it is turned by the wing and flaps. Without the stream of air which flows between the wing and extended flap, the total turning angle of the wings and flaps could not exceed a given angle, for example, ordinarily approximately 28 degrees, without inducing boundary layer separation and endangering the aircraft by reducing lift. Any large cross-sectional structural presence, such as a canoe, which is positioned between the airfoil and the flap interferes with the free flow of the refreshing airstream, and results in reduced flap efficiency. One further shortcoming of large structural fairings or "canoes" is that with the flaps retracted and the aircraft flying at relatively high speeds the canoes create higher aerodynamic drag, resulting in higher fuel consumption, and reduced aircraft range.
Alternative flap drive assemblies have been proposed which attempt to address a selected few of the problems associated with the canoe-style flap drives. For example, U.S. Pat. No. 5,161,757 to Large teaches a bent shaft flap drive wherein the rear flap is mounted on an elongate shaft which extends linearly from within the fixed airfoil to the surface of the deployable flap. The portion of the shaft which extends into the structure of the flap is bent at an angle and fitted with a set of rollers so that it may rotate with respect to the inside of the flap. As the elongate shaft is extended from the airfoil to deploy the flap away from the wing, it is simultaneously rotated by an actuator mounted within the wing which causes the flap to rotate about an axis parallel to the wing line. Large addresses the problems of complexity and exposing large cross-sectional surfaces to the airflow which passes between the extended flap and the fixed wing. Large does not, however, resolve the volumetric concerns within the fixed airfoil nor is it as reliable a system as is desirable in commercial aircraft.
Another disclosure which attempts to avoid excessive disturbances of the airflow between the extended flap and the fixed airfoil is disclosed in U.S. Pat. No. 5,230,487 to Gartelmann et al. Gartelmann teaches a drive and guide mechanism for a flap having three sets of interlocking rods and lever arms, a wheeled carriage journaled to a track within the fixed wing, and a complex set of joints and drive motors all mounted within the wing box of the fixed airfoil. While presenting a reduced surface area to the airflow between the airfoil and the flap, the reference fails to address the concerns of volumetric restriction, complexity, and reliability.
Both U.S. Pat. No. 4,605,187 to Stephenson and U.S. Pat. No. 4,247,066 to Frost et al. disclose wing flap deploying mechanisms which have addressed these problems as well. Both publications, however, teach complex assemblies with many component parts, and which require that considerably larger volumetric regions be reserved for them. In addition, Stephenson teaches an internally disposed apparatus which, upon extension of the flap exposes a considerable aerodynamic cross section to the air which flows between the fixed wing and the deployed flap. Frost teaches a bendable truss structure which simply does not provide any region between the flap and the wing through which air may flow to refresh the boundary layer and assist the air flow turning across the wing.
The principal objects of the present invention are:
(1) to provide a flap drive system which reduces external fairings, or "canoes," thereby reducing aerodynamic drag, and by extension, requisite fuel consumption; PA1 (2) to provide a flap drive system having fewer component parts, and by extension a lower cost, than known flap drive systems; PA1 (3) to provide a flap drive system which occupies a comparably smaller region within the airfoil to reduce volumetric interference with apparati housed therein, i.e. landing gear; and PA1 (4) to provide a flap drive system which is efficient, effective and reliable in operation, and is easy to maintain.